nvk: Support A4B4G4R4 EXT_4444_formats
The following tests, previously not supported, now pass:
dEQP-VK.texture.filtering.2d.formats.a4b4g4r4_unorm.nearest
dEQP-VK.texture.filtering.2d.formats.a4b4g4r4_unorm.linear
dEQP-VK.texture.filtering.2d.formats.a4b4g4r4_unorm.nearest_mipmap_nearest
dEQP-VK.texture.filtering.2d.formats.a4b4g4r4_unorm.linear_mipmap_nearest
dEQP-VK.texture.filtering.2d.formats.a4b4g4r4_unorm.nearest_mipmap_linear
dEQP-VK.texture.filtering.2d.formats.a4b4g4r4_unorm.linear_mipmap_linear
Closes: #36 (closed)
Edited by Rebecca Mckeever